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Biomedical subjects

M Okamoto

Publications and source records attributed to M Okamoto.

At least 919 records · Page 51Linked to original sources
PubMed1986

Changes in intracellular Ca2+ distribution of rat peritoneal mast cells before and after histamine release.

Rat peritoneal mast cells were stained with quin 2, a fluorescent Ca2+ chelator. By means of a fluorescence microscope and real time image processer, it was revealed that the fluorescence derived from the Ca-quin 2 complex was weak in the area occupied by the nucleus and distributed unevenly in the cytoplasm of the resting cells so as to encompass the individual granules. When compound 48/80 or substance P was added in a Ca-free medium, the fluorescence intensity of quin 2 increased markedly all over the cell, suggesting that a large amount of Ca2+ was released from intracellular Ca stores. The increase in the fluorescence intensity produced by compound 48/80 or substance P in a Ca-free medium was inhibited by pretreatment with certain drugs eliciting an increase of c-AMP levels, such as dibutyryl c-AMP and theophylline, or by some anti-allergic drugs providing a membrane stabilizing action.

Aminoquinolines↗
PubMed1986

The risk of neurological impairment of infants failing audiological screening by Crib-O-Gram.

The risk of neurological impairment of those infants failing the Crib-O-Gram hearing screening test was studied. Of the 1,727 infants who were at risk with hearing loss and who were screened by Crib-O-Gram at nurseries for the newborn and premature, 292 (16.9%) failed the screening test. As a control group, whose developmental prognosis was compared with that of the group which failed, 292 infants were selected whose birth dates were very close to the birth dates of those infants failing the test. All of them had passed their Crib-O-Gram screening test. After more than 9 months of follow-up, 28 neurological deficit children were detected in the group failing the test. In the control group, there were 12 neurological deficit children. There was a statistical significance between the two groups (p less than 0.01). Of the 292 infants in the group which failed the test, 231 eventually passed a screening while 43 infants did not. Follow-up examinations of these 43 infants revealed that 15 (34.9%) had neurological deficits. These results show that infants who fail the hearing screening by Crib-O-Gram may have a high probability of neurological deficit and should receive careful follow-up both neurologically and audiologically.

Birth Weight↗
PubMed1986

Semiquantitative grading of severity of mitral regurgitation by real-time two-dimensional Doppler flow imaging technique.

An attempt was made to determine whether mitral regurgitation could be detected and its severity evaluated semiquantitatively by newly developed real-time two-dimensional Doppler flow imaging in 109 patients who underwent left ventriculography. In the Doppler flow imaging technique, Doppler signals due to blood flow in the cardiac chambers are processed using a high speed autocorrelation technique, so that the direction, velocity and turbulence of the intracardiac blood flow are displayed in the color-coded mode on the monochrome B-mode echocardiogram in real time. Mitral regurgitant flow was imaged as a jet spurting out from the mitral valve orifice into the left atrial cavity. It was noted that the regurgitant jet in the left atrial cavity had a variety of orientations and dynamic features when studied by the present technique. The sensitivity of the technique in the detection of mitral regurgitation was 86% as compared with that of left ventriculography. Mitral regurgitation in the false negative cases was mostly mild. On the basis of the farthest distance reached by the regurgitant flow signal from the mitral valve orifice, the severity of regurgitation was graded on a four point scale and these results were compared with those of angiography. A significant correlation (r = 0.87) was found between Doppler imaging and angiography in the evaluation of the severity of mitral regurgitation. A similar result was obtained for the evaluation based on the area covered by the regurgitant signals in the left atrial cavity. Thus, noninvasive semiquantitative evaluation by real-time two-dimensional Doppler flow imaging appears to be a promising clinical technique.

Adolescent↗
PubMed1986

Right atrial flow topography in healthy subjects studied with real-time two-dimensional Doppler flow imaging technique.

The pattern of normal blood flow in the right atrial cavity was studied using the newly developed real-time two-dimensional Doppler flow imaging technique as a standard reference for the Doppler diagnosis of heart diseases with intracardiac shunts at the atrial level. The study was performed primarily with use of the apical four chamber and the parasternal right ventricular inflow tract views in 21 healthy subjects. The following patterns were observed: blood from the inferior vena cava flowed up along the posterior wall of the right atrium and joined with blood from the superior vena cava in the posterocranial part of the right atrial cavity; the flow then coursed along the roof of the right atrium toward the tricuspid valve in the atrial relaxation phase. This flow was always noted along the interatrial septum in the four chamber view. During and after mid-systole of the right ventricle, additional blood flow away from the tricuspid valve appeared, moving from the valve to the central part of the right atrial cavity, that is, at the lower right of the preceding inflow; this flow was interpreted as arising from eddy currents caused by the preceding inflow. In early diastole of the right ventricle, the flow signal area along the interatrial septum and the roof of the right atrium extended into the right ventricular cavity through the tricuspid valve. In the atrial contraction phase only the blood near the tricuspid valve in the right atrial cavity appeared to flow into the right ventricular cavity. Inflow from the coronary sinus was almost undetectable.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Effect of calmodulin on aldosterone synthesis by a cytochrome P-45011 beta-reconstituted system from bovine adrenocortical mitochondria.

Bovine adrenocortical calmodulin was purified and its general properties were examined. The latter were similar to those of bovine brain calmodulin. When added to a cytochrome P-450(11)beta-reconstituted system in the presence of dilauroylphosphatidylcholine, calmodulin decreased the rate of aldosterone production from corticosterone from 0.8 to 0.1 nmol/(min X nmol P-450), while it increased the rate of 18-hydroxycorticosterone production from 1.8 to 4.6 nmol/(min X nmol P-450). This effect of calmodulin on steroid production was maximum at a concentration of 1 microM, when 1 microM cytochrome P-450(11)beta was used. The effect was dependent on the presence of Ca2+, and maximal response was observed at less than 1 microM Ca2+. There was essentially no difference in the effect when bovine brain calmodulin was used. Calmodulin induced a change in the activity of cytochrome P-450(11)beta in the presence of a wide concentration range of corticosterone as a substrate. As for 18-hydroxycorticosterone production, calmodulin increased both the maximal activity and the apparent Km for corticosterone, but it decreased the apparent Km for adrenodoxin. Adrenodoxin at a concentration of less than 20 microM did not fully abolish the effect of calmodulin. A small type I difference spectrum appeared when calmodulin was added to cytochrome P-450(11)beta. The difference spectrum increased significantly in the presence of both Ca2+ and adrenodoxin. These results suggest that calmodulin interacts with cytochrome P-450(11)beta in the presence of adrenodoxin and then modulates the activity of aldosterone synthesis catalyzed by cytochrome P-450(11) beta.

Adrenal Cortex↗
PubMed1986

Molecular cloning and sequence analysis of full-length cDNA for rabbit liver NADPH-cytochrome P-450 reductase mRNA.

The nucleotide sequence of the mRNA for NADPH-cytochrome P-450 reductase from rabbit liver was determined from a full-length cDNA clone (pFP105). The clone contains 2,269 nucleotides complementary to rabbit liver reductase mRNA. The single open reading frame of 2,037 nucleotides codes for a 679-amino acid polypeptide with a calculated molecular weight of 76,583 daltons. The cloned cDNA contains the complete 3'-noncoding region of 193 nucleotides, including 68 nucleotides of poly(A), and 39 nucleotides of the 5'-noncoding region. The nucleotide sequence in the coding region of cDNA of rabbit reductase (pFP105) showed 85% homology to that of rat reductase (Porter, T.D. & Kasper, C.B. (1985) Proc. Natl. Acad. Sci. U.S. 82, 973-977, and Murakami, H. et al. (1986) DNA 5, 1-10). Rabbit reductase has one more amino acid residue than the rat enzyme, and the amino acid compositions of the two enzymes are similar. The amino acid sequence of the rabbit enzyme showed 91% identity with that of the rat enzyme. The segment related to binding of FMN and FAD was well conserved among rabbit, rat, and pig reductases. The sequence related to AMP moiety-binding was also conserved among these species, and was found in the amino acid sequence of NADH-cytochrome b5 reductase, another flavoenzyme in the microsomal electron transport system.

Amino Acid Sequence↗
PubMed1986

Analysis of debromination of 1,2-dibromoethane by cytochrome P-450-linked hydroxylation systems as observed by bromide electrode.

Debromination of 1,2-dibromoethane (DBE) by a rabbit liver microsomal preparation and a reconstituted cytochrome P-450 enzyme system was investigated. The reaction was performed in our newly constructed reaction vessel, in which a bromide electrode was installed. During the reaction, the liberated bromide ion was continuously measured by the bromide electrode, and the amount was recorded. In the microsomal preparation, the DBE-debromination rate per nmol cytochrome P-450 was enhanced by phenobarbital-pretreatment of rabbits compared with the untreated microsomes, whereas it was diminished by 3-methylcholanthrene-pretreatment. The debromination reaction was reconstituted in a purified enzyme system containing phenobarbital-inducible rabbit liver microsomal cytochrome P-450 (P-450PB), NADPH-cytochrome P-450 reductase, and NADPH. The optimum conditions required the presence of dilauroylphosphatidylcholine and cytochrome b5. Cytochrome b5 was found not to be an obligatory component for the DBE-debromination in the reconstituted system, but it stimulated the activity about 3.4-fold. Preincubation of the reconstituted mixture with guinea pig anti-cytochrome P-450PB antiserum markedly inhibited the debromination reaction.

Animals↗
PubMed1986

Dog and rat pancreatic phospholipases A2: complete amino acid sequences deduced from complementary DNAs.

We performed molecular cloning of the cDNAs that encode dog and rat pancreatic phospholipases A2 to predict the primary structures of these enzymes. The deduced amino acid sequences exhibited a highly conservative feature which is common to a group of pancreatic phospholipases A2 from various animal species. Furthermore, the structures of the signal sequences of dog and rat pancreatic phospholipases A2 were predicted, although the assignment of the positions cleaved post-translationally is only tentative at the present time.

Amino Acid Sequence↗
PubMed1986

Change in brain thyrotropin-releasing hormone (TRH) mechanism of amygdaloid kindled rats.

We reported previously that DN-1417, a potent analog of thyrotropin-releasing hormone (TRH), suppressed both the progression of amygdaloid (AM) kindling and AM kindled seizure. To study a functional role of the cerebral TRH mechanism in AM kindling, immunoreactive TRH (IR-TRH) and specific TRH receptor binding were examined in the rat brains kindled from the left AM. The IR-TRH concentration elevated significantly in the amygdala plus piriform cortex and the hippocampus 24 and 48 hours after the AM kindled convulsion. Such an elevation of IR-TRH was not found 7 days after the last convulsion, indicating that the elevation of IR-TRH was a transient change seen after the AM kindled convulsion. By contrast, the specific TRH receptor binding in the striatum increased 48 hours, 7 and 21 days after the AM kindled convulsion. This indicates that the increase of the specific TRH binding in the striatum was a long-lasting change. The present study suggests that the change in the striatal TRH receptors may be associated with a long-lasting seizure susceptibility of AM kindled rats.

Amygdala↗
PubMed1986

Autophosphorylation and kinase activity of insulin receptor in diabetic rats.

Insulin resistance is observed in insulin-deficient diabetic states in spite of an increase in insulin binding to its target cells. To characterize this type of insulin resistance, autophosphorylation and kinase activity of the insulin receptor on liver was studied with streptozotocin (STZ)-induced and BB diabetic rats. Insulin binding capacity was increased in proportion to the severity of the diabetic state in the STZ rat. In the diabetic BB rat, the insulin binding capacity was also increased, and this was partially normalized by insulin treatment. By contrast, insulin-stimulated autophosphorylation of the beta-subunit of the insulin receptor was decreased in proportion to the severity of the diabetic state in the STZ rat. Peptide mapping by reverse-phase high-performance liquid chromatography revealed a decrease in labeling at all sites of autophosphorylation. Kinase activity of the insulin receptor to exogenous substrates was also decreased in proportion to the diabetic state. In the BB rat, autophosphorylation and kinase activity of the insulin receptor were both decreased in the diabetic state and partially normalized by insulin treatment. In addition to the beta-subunit of insulin receptor, a 170 kdalton phosphotyrosine-containing protein was also identified in the glycoprotein fraction of liver. Although the phosphorylation of this protein was not insulin dependent, it was decreased markedly in the diabetic state. This protein is immunologically distinct from the insulin receptor, but is rich in phosphotyrosine. Based on its size and phosphotyrosine content, this protein may be the epidermal growth factor receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Purification and some properties of membrane-associated phospholipase A2 of human spleen.

Membrane-associated phospholipase A2 was purified to homogeneity from human spleen. The enzyme was solubilized from the particulate fraction by the addition of KBr, and purified by reverse-phase high-performance liquid chromatography. The estimated molecular weight of the enzyme was 14,000. The enzyme had a pH optimum around 9.5, required the presence of Ca2+ for its activity, and hydrolyzed phosphatidylethanolamine more efficiently than phosphatidylcholine.

Calcium↗
PubMed1986

The effect of steroidal and nonsteroidal anti-inflammatory agents on granulocyte migration into bovine pulmonary artery intimal explants.

To determine whether steroidal or non-steroidal anti-inflammatory agents inhibit granulocyte migration, we measured granulocyte adherence to and migration across the intact endothelial layer of bovine pulmonary artery intimal explants. Explants were placed endothelium uppermost in chemotaxis chamber with either fetal calf serum (FCS) or zymosan activated plasma (ZAP) in medium 199 in the lower well and 5 X 10(6) separated 51Cr labelled granulocytes/ml in medium 199 + FCS in the upper well. Methylprednisolone (0.3 and 3.0 mg/ml), indomethacin (5 and 50 microM) and ibuprofen (10 and 100 microM) were also added to the upper well of some chambers. After 30, 60, 120 or 180 minutes of incubation the chambers were dismantled. Granulocyte adherence was assessed by rinsing the explant in 0.1% trypsin; the number of radioactive counts in the trypsin wash represented the number of adherent cells. Those remaining in the explant represented the number of granulocytes that migrated into the explant. At each time studied, chemotaxin-induced granulocyte migration was 2-3 times that of unstimulated or random migration (180 min incubation with FCS = 30.5% +/- S.E. 2.1; with ZAP in lower well = 61.6 +/- 3.4). Both unstimulated and chemotaxin-induced migration was significantly decreased from 30 minutes by 3.0 mg/ml of methylprednisolone (180 min incubation with ZAP in lower well = 22.3 +/- 5.8), but not by 0.3 mg/ml. However, one hour pretreatment of either the granulocytes or the explant with 3.0 mg/ml methylprednisolone had no significant effect on granulocyte migration. In contrast, granulocyte migration was unaltered by treatment with either indomethacin or ibuprofen. Methylprednisolone, indomethacin and ibuprofen had little effect on granulocyte adherence. We conclude that granulocyte migration across an intact endothelial layer is inhibited by high dose corticosteroids but not by cyclooxygenase inhibitors. This suggests a plausible rationale for use of high doses of corticosteroids in clinical states where granulocytes may mediate tissue injury.

Animals↗
PubMed1986

FR-900452, a specific antagonist of platelet activating factor (PAF) produced by Streptomyces phaeofaciens. I. Taxonomy, fermentation, isolation, and physico-chemical and biological characteristics.

A PAF antagonist, designated as FR-900452, was isolated from fermentation products of Streptomyces phaeofaciens and the molecular formula was determined as C22H25N3O3S. The compound inhibited PAF-induced rabbit platelet aggregation with an IC50 of 3.7 X 10(-7)M, but was much less active against collagen-, arachidonic acid- or ADP-induced aggregation (IC50; 6.4 X 10(-5), greater than 10(-4) or greater than 10(-4)M, respectively).

Adenosine Diphosphate↗